Needs for increased functionality, capacity and performance of integrated circuits of a given chip size and increased economy of manufacture have driven the size of electronic elements thereof to extremely small sizes and extremely high integration densities. Small size of active and passive electrical components allows increased integration density and increased numbers of electrical devices on a chip of given area for increased functionality. High integration density allows interconnections to be of reduced length which supports higher clock rates of operation while reducing susceptibility to noise. However, such small sizes and high numbers of electronic elements has greatly increased the accuracy with which such elements must be formed. For example, it is known that tools such as process chambers for integrated circuit manufacture are not precisely uniform over the entire processing area of a wafer and allow small variations in the rate at which various processes such as etching are performed across the area of a semiconductor wafer from which many concurrently formed chips are later diced. Further, deposition and etching processes are known to be affected by chip design since differing densities of elements and areas for deposition and etching can locally concentrate and/or deplete etchant or material precursor concentrations. Both of these effects are becoming significant at current and foreseeable integration densities and electronic element sizes. At the present state of the lithographic art for semiconductor manufacture, variations in structures due to such non-uniformity of the progress of material deposition and removal processes can cause defects of sufficient severity to significantly reduce manufacturing yield.
While all types of semiconductor devices are potentially subject to such problems, high density memory arrays and processors having embedded memory arrays are particularly subject to the occurrence of such defects and consequent loss of manufacturing yield. This susceptibility to loss of manufacturing yield is principally due to the need for maximum possible memory capacity requiring extremely high density of capacitors formed at or near the limits of lithographic resolution which also contributes to lack of process uniformity across the chip and wafer areas. Deep trench storage capacitors which include a dielectric material having a particularly high dielectric constant to increase capacitance and which are metal filled for high write, erase, sense and refresh speeds have been found to be particularly susceptible to such defects and compromise of manufacturing yield. It has also been recently observed that such storage capacitor structures are particularly sensitive to overlay errors, especially when forming connections between electrodes when the deep trench capacitors are optimally nested for extreme integration density.